1. Technical Field
The present invention relates to compounds suitable for use in magnetoelectronics.
2. Description of Related Art
Magnetoelectronics is a new field of electronics involving electronic components that employ magnetoresistance effects and spin-polarized electrons, or will employ them in the future. Due to their magnetoresistive properties, such compounds may be employed as, among other things, magnetic-field sensors. The “magnetoresistive properties” involved are a change in electrical resistivity induced by an external magnetic field (magnetoresistance). Due to the spin-polarized tunneling that occurs at room temperature, such compounds may also be employed as basic building blocks in fabricating magnetic random-access memories (MRAM) and spin transistors. “Spin-polarized tunneling” is defined as tunneling (quantum-mechanical penetration of a potential barrier) of electrons, where the probability that tunneling will occur depends upon their spin polarization.
Magnetic-field sensors are used on the magnetic heads of hard-disk drives that are employed as, e.g., external computer storage devices. Conventional magnetic heads detect the strengths and directions of magnetic fields based on a current induced in a coil. However, as recording density increases, the space available for recording a bit decreases, and the resultant magnetic fields will gradually decrease. Ultraresponsive magnetic-field sensors that cannot be manufactured using conventional technologies are required for detecting such weak external magnetic fields. Ultraresponsive magnetic-field sensors that utilize giant magnetoresistance (GMR) or tunneling magnetoresistance (TMR) are known (cf. S. Mengel: “Innovationspotential Magnetoelektronik,” Physikalische Blätter 55 (3) (1999), pp. 53-56). Magnetic-field sensors that exhibit magnetoresistive effects at temperatures around 200° C. are employed in the automotive industry. Although utilizing colossal magnetoresistance (CMR) in compounds, such as manganese oxides, allows attaining effects that are several orders of magnitude greater, that approach is not yet of technological interest due to the low field responsivities that result.